Sheet rolling method and sheet rolling mill

Abstract

In a rolling method applied to a multi-roll strip rolling mill composed of not less than four rolls, one of the zero point of the roll positioning devices and the deformation characteristic of the strip rolling mill or alternatively both the zero point of the roll positioning devices and the deformation characteristic of the strip rolling mill are found from a measured value of the thrust counterforces in the axial direction of the roll acting on at least all the rolls except for the backup rolls in the kiss-roll tightening state and also from a measured value of the roll forces of the backup roll acting on the backup roll chocks of the top and the bottom backup roll in the vertival direction. According to the thus obtained zero point of the roll positioning devices or the deformation characteristic of the strip rolling mill, the setting and control of the roll forces is executed when rolling is carried out.

Description

The present invention relates to a method for rolling a strip made of a metal such as steel, and also relates to a rolling mill therefor.DESCRIPTION OF THE PRIOR ARTIn the case of rolling a metal strip, it is important that the ratio of the elongation, of a workpiece to be rolled, on the work side and on the drive side are made to be equal to each other. When the ratio of elongation on the work side and that on the drive side are different from each other, a defect, such as a camber, and a failure in the dimensional accuracy, such as wedge-shaped strip thickness occur. Further, problems may be caused when a strip is rolled. For example, (lateral) traveling or trail crash of a workpiece to be rolled may be caused in the process of threading.In order to make the ratio of elongation of the workpiece to be rolled on the work side to be the same as that on the drive side, a difference between a position of reduction of a rolling mill on the work side and that on the drive side is adjuste...

AI Technical Summary

Benefits of technology

In this case, the roll chock for supporting a radial load can be composed in such a manner that the inner race of the bearing and the roll shaft are fitted to each other while a clearance is left between them or that a cylindrical roll bearing having no inner race is used. Due to the above arrangement, no thrust force is given to the roll chock for supporting a radial load. By the above arrangement, even when a roll bending force is acting, a small displacement in the axial direction of the top work roll is transmitted to only the chock for supporting thrust counterforces. Therefore, it is possible to reduce disturbance given to the measured value of thrust counterforces, that is, disturbance can be reduced negligibly small.

On the other hand, in the structure in which the chock is not separated from the bottom work roll, unlike the top work roll, when a thrust force acts on the bottom work roll, a frictional force corresponding to a roll bending force is generated between the top and the bottom work roll chock. However, since the chock of the top work roll does not support the thrust force, the top work roll chock is a little displaced in the direction of the thrust force together with the bottom work roll. Finally, thrust counterforces acting on the bottom work roll can be accurately detected via the chock of the bottom work roll.

As described above, by the existence of the slide bearing, the frictional force between the load members of the roll bending force and the roll chock can be greatly reduced, and the measurement accuracy of measuring the thrust counterforces can be greatly enhanced.

This load transmission member is disposed between the load members of the roll bending device and the roll chock with pressure. The mechanical strength of thin skin is sufficiently high so that a liquid film formed inside can not be broken. Since resistance of thin skin to the deformation of out-of-plane is not more than 5% of the maximum value of the roll bending force. Therefore, it is possible to sufficiently reduce an apparent frictional force acting from the load members of the roll bending device with respect to a small displacement of the roll chock in the axial direction. In the case where the aforementioned load transmission member is not arranged, the load members of the roll bending device and the roll chock come into solid contact with each other. Therefore, the coefficient of friction is approximately 30%. On the other hand, in the case where the load transmission member of the invention is inserted, it is possible to neglect the shearing deformation resistance of the liquid film formed inside. Accordingly, an apparent frictional force is not more than 5% of the maximum value of the roll bending force. As a result, the measurement accuracy of measuring thrust counterforces can be greatly enhanced.

When the thrust counterforces in the axial direction of the roll is measured, the roll chock, the thrust counterforces of which is measured, is given a force by the roll balance device or the roll bending device. When this force is made to be not more than 1 / 2 of the roll balance force, or preferably when this force is made to be zero, it becomes possible to accurately measure the thrust counterforces, and it becomes possible to suppress a factor of disturbance with respect to the equation of equilibrium condition of moment acting on the roll. Therefore, it becomes possible to set a roll forces accurately, and also it becomes possible to control a roll forces accurately.

In order to realize a rolling operation in which ratios of elongation on the work and the drive side are made equal to each other, the present invention provides a strip rolling mill calibration method and a strip rolling mill calibration device by which a deformation characteristic of the rolling mill with respect to the asymmetrical load on the upper and lower sides caused by a thrust force generated between the rolls can be accurately identified.

Problems solved by technology

When the ratio of elongation on the work side and that on the drive side are different from each other, a defect, such as a camber, and a failure in the dimensional accuracy, such as wedge-shaped strip thickness occur.

Further, problems may be caused when a strip is rolled.

For example, (lateral) traveling or trail crash of a workpiece to be rolled may be caused in the process of threading.

However, it is impossible to completely solve the above problems of defective quality such as camber and wedge-shaped strip thickness, and also it is impossible to completely solve the above problems of threading, such as (lateral) traveling and pinching, of a trailing end of a workpiece to be rolled.

However, the difference between the load cell load of the rolling mill on the work side and that on the drive side includes various disturbances in addition to an influence caused by (lateral) traveling of the workpiece to be rolled.

However, in the case of rolling a long workpiece or in the case of tandem-rolling, even if leveling is not adjusted appropriately, (lateral) traveling is not caused in many cases because of the weight of the workpiece to be rolled on the upstream side of the rolling mill and also because of a condition of restriction of the workpiece by the rolling mill on the upstream side.

Therefore, according to the above methods disclosed in the Patent Publications, in the case of rolling a long workpiece or in the case of tandem-rolling, it is impossible to detect a quantity of (lateral) traveling although leveling is not adjusted appropriately.

For the above reasons, it is impossible to use any of the above methods as the most appropriate method of controlling the leveling.

When a quantity of (lateral) traveling is directly measured by the above methods, it is impossible to optimize leveling only by these methods.

Further, according to the above methods, a phenomenon occurring in the roll bite is not directly measured.

Therefore, the methods tend to be affected by disturbance, and furthermore a delay is caused in the control of leveling, which is an essential defect of the methods.

However as described above, the difference between the rolling load on the work side and that on the drive side detected by the load cell includes not only a quantity of (lateral) traveling of the workpiece to be rolled but also various disturbance.

For the above reasons, this thrust force becomes a serious disturbance with respect to the object of determing, by the difference between the load measured by the load cells of the rolling mill on the work side and that on the drive side, asymmetry of the rolling load distribution on the work and the drive side.

Therefore, it is very difficult to estimate the thrust force.

In this case, not only the above thrust force between the rolls but also the thrust force between the top and the bottom work roll becomes disturbed.

When the thrust force acts between the rolls at this time as described above and disturbance is included in the difference between the load measured by the load cell on the work side and the load measured by the load cell on the drive side, it becomes impossible to conduct an accurate zero point adjustment of leveling, and this error of zero point adjustment is caused at all times when leveling is conducted after that.

Also in this case, the aforementioned thrust force generated between the rolls could be a serious error factor.

For the above reasons, it is not easy to measure the thrust counterforces.

Therefore, explanations will be made under the condition that it is impossible to obtain a measured value of the thrust counterforces of the backup roll.

Therefore, it becomes impossible to estimate a difference of the distribution of the linear load of the rolls between the work and the drive side.

However, in this case, when a roll forces is quickly changed by the hydraulic cylinder, there is a possibility that a great error occurs in the measured value.

When the above type thrust reaction forces measuring device is used, a roll balance force acting on each roll or a frictional force in the axial direction of the roll caused by a roll bending force could be a serious disturbance when a thrust reaction forces is measured.

In general, it is difficult to measure this frictional force itself.

Therefore, this frictional force becomes a factor of disturbance of the measured thrust counterforces.

However, since the chock of the top work roll does not support the thrust force, the top work roll chock is a little displaced in the direction of the thrust force together with the bottom work roll.

However, in some cases, it is impossible to control the crown profile of a rolled strip at a predetermined value by the above roll balance force or the roll bending force.

However, in the case of a rolling mill having only the roll bending device as a control means for controlling a strip crown and flatness, there is a possibility that a predetermined strip crown and flatness can not be obtained when the above rolling method is adopted.

The above loads which are not symmetrical with respect to the upper and lower sides cannot be balanced only by the internal forces of the rolling mill housings on the work and the drive side.

As a result, the load given to the housing on the work side can not be balanced by the single body of the housing on the work side.

Therefore, for example, it is possible to use an overhead crane as it is, in which it is difficult to accurately measure the external force to be given.

Due to the moment received in this way, there is a possibility that a thrust force is generated by friction on a contact face of the calibration device with the roll of the rolling mill.

This thrust force causes a disturbance to the load cell used for measuring a rolling load.

Therefore, this thrust force also causes a disturbance when the deformation characteristic is determined by giving a load asymmetrical with respect to the upper and lower sides which is an object of the method of calibration of the rolling mill.

However, even if the thrust force can be measured and the thrust force acting on the backup rolls can be measured, it is not clear how the measured thrust force has an influence on the load cell load.

However, the backup roll is given a heavy load from not only the keeper strip but also the roll positioning devices and the roll balance device.

However, as described later, the present device of calibration is not necessarily used under the condition that the thrust force acting on the top roll and the thrust force acting on the bottom roll are balanced with each other.

However, not only the resultant force of the thrust counterforces but also a frictional force in the vertical direction following this resultant force acts between the above fixing members and the support member for supporting the thrust counterforces of the calibration device.

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